Exhaust gas sensor and method of producing the same

Abstract

An exhaust gas sensor which is exposed to exhaust gas, includes a measuring electrode; and a porous ceramic coating provided on the measuring electrode and comprised of at least two layers, a first porous ceramic layer which is provided on the measuring electrode and at least a second porous ceramic layer which is provided on the first porous ceramic layer and which is directly exposed to the exhaust gas, wherein the first porous ceramic layer contains getter substances for removal of substances that are harmful to the measuring electrode, and wherein the second porous ceramic layer is provided with one of a diffusion resistance or a catalytic effect relative to exhaust gas constituents such that, at the boundary of the first and second porous ceramic layers, a gas composition is present in use which is comprised of one of oxidizable or reducible gas constituents and which sets a control position for the exhaust gas sensor.

What is claimed is: 
     
       1. An exhaust gas sensor which is exposed to exhaust gas, comprising: a measuring electrode; and   a porous ceramic coating provided on the measuring electrode and comprised of at least two layers, a first porous ceramic layer which is provided on the measuring electrode and at least a second porous ceramic layer which is provided on the first porous ceramic layer and which is directly exposed to the exhaust gas,   wherein the first porous ceramic layer contains getter substances for removal of substances that are harmful to the measuring electrode, and   wherein the second porous ceramic layer is provided with one of a diffusion resistance or a catalytic effect relative to exhaust gas constituents such that, at the boundary of the first and second porous ceramic layers, a gas composition is present in use which is comprised of one of oxidizable or reducible gas constituents and which sets a control position for the exhaust gas sensor.   
     
     
       2. The exhaust gas sensor as defined in claim 1, wherein the measuring electrode is a solid electrolyte sensor having at least one catalytically active measuring electrode. 
     
     
       3. The exhaust gas sensor as defined in claim 1, wherein the measuring electrode is a resistance sensor having a resistance layer which is positioned between the first porous ceramic layer and the measuring electrode, and which has solid-state characteristics which change as a function of concentration of the exhaust gas constituents. 
     
     
       4. The exhaust gas sensor as defined in claim 1, wherein the first porous ceramic layer is provided with at least one getter substance selected from the group consisting of precious metals, precious-metal oxides, and precious-metal alloys. 
     
     
       5. The exhaust gas sensor as defined in claim 1, wherein the second porous ceramic layer contains at least one catalytic converter material for setting of a thermodynamic equilibrium in use.